The present invention relates to the data search operation of an optical head which performs a data search in a magneto-optical disk driver and, more particularly, to an optical disk high-speed search control device and method thereof which counts the number of tracks when the optical head searches the information while being driven by a voice coil motor, so as to reach the target track.
As an external memory device for a computer, optical disk devices are in wide use since the data search speed is higher than the access time of other memory devices (e.g., magnetic tape), while its memory capacity is larger. Also, the recording medium for such external memory devices can be easily exchanged.
However, a magneto-optical disk driver is hard to move at high speeds since the structure of a signal detector in the driver is more complicated and heavier than that of a magnetic disk driver. Moreover, the track pitch of an optical disk is narrow (1.6 .mu.m), with adjacent tracks being extremely close to each other, while the amount of eccentricity for spinning the disk is approximately 50 .mu.m. In order to reach the target track, a method which combines a coarse seek method and a fine seek method is used, with the coarse seek method performing the majority of the movement by positioning the optical head near the target track. The fine seek method forces the optical pickup to jump inward or outward from the current track, as much as the amount of the remaining track using an actuator installed within the optical head, and moves the lens toward the target track, so the pickup can ultimately reach the target track. This track-jump handling is done by applying a jump pulse to a tracking actuator.
FIG. 1 is a block diagram of the conventional optical disk high-speed search control device. The device comprises: a location information detector 112 which reads the location information detected by an optical pickup; a speed converter 113 which shapes and doubles a waveform of a signal which corresponds to the location from location information detector 112; a speed/voltage converter 114 which transforms the above waveform which is converted by speed converter 113 into a driving voltage; a location detection counter 116 which counts in order to detect a location from the waveform converted by speed converter 113; and a reference speed signal generator 117 which generates a reference speed signal for controlling the spinning of a disk according to the track jump command using the above location detection signal counted by location detection counter 116; and a digital-to-analog (D/A) converter 115 which converts the speed information generated from reference speed signal generator 117 into an analog signal.
Referring to FIG. 1, the driving method of the conventional optical disk high-speed search control device as constructed above will be explained in detail.
Location information detector 112 reads by linear spacing the location information detected by an optical pickup, and speed converter 113 shapes and doubles the location information detected from location information detector 112.
The signal converted in speed converter 113 is converted into a voltage in speed/voltage converter 114. Location detection counter 116 counts in order to detect the location from the converted waveform through speed converter 113. After the counting, reference speed signal generator 117 forms the counted signal into speed data which corresponds to the number of tracks counted up to the target track according to a track jump command. Also, the digital speed data is converted to an analog signal by digital-to-analog converter 115 in order to drive a signal detecting driving motor (not shown) and is then output. The motor driving signal is formed by the difference between the voltage which is output from speed/voltage converter 114 and the output motor driving voltage.
Using the data search method in accordance with the conventional optical disk high-speed search control device, the desired target track is difficult to reach correctly with just one driving operation, since the track has an eccentricity caused by the instrumental problem of location information detecting means driven by the aforementioned linear scale. As a result, the time required for fine seek is approximately 20 ms.about.30 ms, which impedes the realization of high speed access.